1. Field of the Invention
The present invention relates to semiconductor structures and fabrication methods thereof, and more particularly, to a semiconductor package structure and a fabrication method thereof.
2. Description of Related Art
As electronic products are developed toward miniaturization, less space is available on surfaces of printed circuit boards for mounting semiconductor packages. Therefore, a 3D stacking technique is developed, which allows at least two semiconductor package to be stacked on one another to form a PoP (package on package) structure. Such a PoP structure meets the demand for high-density mounting of components of electronic products.
FIG. 1 is a schematic cross-sectional view of a conventional semiconductor package of a PoP structure. Referring to FIG. 1, a semiconductor chip 11 having opposite active and inactive surfaces is provided and an encapsulant 12 is formed around the semiconductor chip 11. A redistribution layer 13 is formed on the active surface of the semiconductor chip 11 and a circuit layer 16 is formed on the inactive surface of the semiconductor chip 11. The circuit layer 16 and the redistribution layer 13 are electrically connected through a plurality of conductive through holes 15 formed in the encapsulant 12. Further, a plurality of solder balls 14 are formed on the redistribution layer 13.
To form the conductive through holes 15 in the encapsulant 12, a laser drilling process is generally performed to form through holes in the encapsulant 12 first and then an electroplating process is performed to form the conductive through holes 15 in the through holes. However, filler particles that are usually contained in the encapsulant 12 increase surface roughness of the through holes, thereby increasing the difficulty of the electroplating process and easily resulting in electrical discontinuity. On the other hand, the size of the filler particles may be reduced to reduce the surface roughness of the through holes. But such a reduction in the size of the filler particles also reduces the strength of the package structure.
Therefore, there is a need to provide a package structure and a fabrication method thereof so as to overcome the above-described drawbacks.